Esters isomers

Draw and name five ester isomers that have the molecular formula C5H10O2. 

Preliminary results from a study of catalytic activation of the heterocoupling between arylhalides and alkenes using pony-tail-functionalized dendrimer-encapsulated Pd nanoparticles have shown promise. For example, the classic Pd-catalyzed Heck coupling between arylhalides and methacrylate yields predominately (> 97%) the trans-cinnimaldehyde product [176]. On the other hand, the C02-soluble dendrimer nanocomposite exclusively catalyzes the production of the highly unfavored 2-phenyl-acrylic acid methyl ester isomer at 5000 psi and 75 °C (Fig. 27] [177]. 

Several thieno[2,3-c]- and -[3,2-r ]-thiopyranthione ester isomers, 40 and 41, have been studied by X-ray analysis and their electronic spectra have been recorded <20050L791>. 

The partial synthesis of a Ci8 dimethyl furanoid ester (29) from methyl linoleate and from methyl 10,13-epoxy-ll-methyloctadeca-10,12-dienoate has been described (Scheme 5) (81CC1110). Treatment of methyl linoleate (23) with MCPBA gave the methyl 9,12-diepoxystearate (24), which was easily converted to a mixture of the two C18 furanoid fatty ester isomers (25). TTie corresponding methyl dioxostearates (26) were methylated to... 

Se = C(C6H4R-p)H ] (R = H, OMe, CF3) with bis( -butylthio)ethyne. The structure of one 2H-selenete complex 132 (R = H) was confirmed by an X-ray structural analysis.247 Based on spectra of these compounds, an equilibrium between the 2H-selenete complexes (132) and their thioselono-carboxylic ester isomers (133) was proposed (Scheme 36). The fraction of 133 in the eqilibrium was estimated to be about 6-10%. Decomplexation of the heterocyclic ligand in 132 (R = H) with [NEt4]Br afforded the first uncoordinated 2//-selenete. In addition, a 3,4-dihydro-l,2-diselenine was obtained.247... 

The pyrrolidinyl enamino keto-diester 77 reacted with 3-hydrazinylpropan-l-amine in the presence of 1 N HC1 to afford the pyrazolodiazepine 78, a key intermediate in the preparation of a glycoprotein Ilb/IIIa antagonist, in 40% yield (Scheme 35) <2003TL5867>. The requirement for the presence of 1 N HC1 to promote this process suggested that the diketo diester is the actual intermediate in the process, evaluated by examining the outcome with a mixed methyl/ethyl ester. The product was isolated as a 1 1 mixture of ester isomers, consistent with the intervention of a hydrolytic step that led to symmetrization of the electrophile. 

The regioselective anti-Markovnikov addition of benzoic acid to phenyl-acetylene has also been carried out with success at 111 °C in the presence of ruthenium complexes containing a tris(pyrazolyl)borate (Tp) ligand [RuCl(Tp)(cod), RuCl(Tp)(pyridine), RuCl(Tp)(N,N,Ar,AT-tetramethylethyl-enediamine )] with a stereoselectivity in favour of the (E)-enol ester isomer [22]. The o-enynyl complex Ru(Tp)[PhC=C(Ph)C=CPh](PMe/-Pr2) (C) efficiently catalyses the regioselective cyclization of a,cu-alkynoic acids to give en-docyclic enol lactones [23] (Eq. 2). 

Two homophthalic ester isomers are ordinarily generated when reacting diethylmalonate with an insitu benzyne intermediate as illustrated in Eq. 1 ... 

Enolates from A-(diphenylmethylene)glycine esters (211) were also used as nucleophiles in Mannich reactions with chiral A-sulhnyl imines (212), as reported by Davis and coworkers (equation 56f. They found that the simple antUsyn selectivity of the formed 2,3-diamino esters 213 and 214 was strongly influenced by the water content in the THE solvent. In the absence of water both 2,3-diamino ester isomers were equally obtained (first entry of Table 18), but by changing the H2O/LDA ratio the formation of the... 

An example of application of this method is the separation of the C-27 glycosyl ester of quinovic acid from its C-28 glycosyl ester isomers from U. tomentosa (4) and G. platypoda (5). 

Accordingly, treatment of 129 with potassium f-butoxide and pseudoacid 107 gave a 58% yield of the required ( ,Z)-muconic ester 130. Macrolactonization was then achieved via the mixed pivaloyl anhydride in the presence of 4-pyrrolidinopyridine to afford verrucarin (124) in 60% yield along with its ( , )-muconate isomer 131 (30%). The latter could be isomerized with 12 in benzene to provide additional 124 (61%) contaminated with another muconic ester isomer. 

Which of the above acids does not have an ester isomer ... 

Lie Ken Jie, M.S.F., Syed-Rahmatullah, M.S.K., Lam, C.K., and Kalluri, P. (1994) Ultrasound in Fatty Acid Chemistry Synthesis of a 1-Pyrroline Fatty Acid Ester Isomer from Methyl Ricinoleate, Lipids 29, 889-892. 

Carbon Atoms Ketone Isomers Ester Isomers... 

Fig. 6.7 shows the CIMS/MS spectrum for llr,13r-18 2 with an a/ ratio of 1.5. The mass spectrum identifies this isomer as either a cisicis or a trans trans CLA, and the elution profile allows unambiguous identification of this isomer as the trans trans one. Other CLA methyl ester isomers coeluted after this compound in a single peak. Their elution order, relative to the other already identified CLA methyl esters, indicates that they are trans trans isomers. The confirmation of their double... 

As a final set of examples, enantioselective allylic substitution of unstabilized eno-lates to form a new stereocenter at the enolate carbon have been developed through the decarboxylative reactions of allyl enol carbonates. - - These reactions are enantioselective versions of reactions closely related to those in Equation 20.18 and Scheme 20.4, and two examples are shown in Equations 20.60 and 20.61. In these cases, a new stereocenter is formed at the a-carbon of the enolate nucleophile. Most of these reactions have been conducted with allyl enol carbonates that generate cyclic ketone enolates, but enantioselective reactions of acyclic allyl enol carbonates have also been reported. Although allyl enol carbonates undergo decarboxylation faster than the 3-keto ester isomers, the 0-allyl p-keto esters are more difficult to prepare, and enantioselective allylations starting with p-ketoesters have been reported. - Decarboxylative reactions of amines and a-amino acids have been conducted to form allylic and homoallylic amines (Equation 20.62), respectively, and enantioselective decarboxylative allylations of amides have been reportedIridium-catalyzed enantioselective decarboxylative allylation of amides starting with 0-allyl imides has also been reported. ... 

In a synthesis of conformationally restricted LTB4 analogues 249 [54], the mono-protected diol diastereomers 250 and 251 were subjected to the conditions of a Claisen-Johnson rearrangement. Classical reaction conditions afforded the expected ester isomers 252 and 253, respectively (Scheme 6.40). 

Racemic Malolactonate. The first cyclic monomer prepared was the benzyl ester of the 3-lactone of malic acid. Initial attempts to make the lactone directly from malic acid itself were unsuccessful, so bromosuccinic acid was chosen as the starting material. This compound was converted to its anhydride by refluxing in acetyl chloride, and the anhydride was reacted with benzyl alcohol to yield a mixture of the two bromosuccinic acid monobenzyl ester isomers. Only one of these esters, IIIB, is capable of being converted to the lactone by... 

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